A new staining procedure for electron microscopical cytology

Abstract

A new staining method for ultrathin sections is proposed, which gives preferential contrast to certain cell structures. The tissues are fixed with aldehyde and embedded in Epon or GMA. The staining is based on the use of chelating agents. After brief prestaining with uranyl acetate, the thin sections are floated for various lengths of time on McIlvaine buffer (0.2 M or less) or on EDTA (0.2 M or less). After this treatment, poststaining with lead citrate reveals a heavy contrast of cell structures known to contain RNA, whereas deoxyribonucleoproteins have lost most or all of the stain. Several exceptions to this rule are indicated. This procedure has the character of a regressive stain, where the chelating agents seem to play the role of differentiators.